Technical Field
The present disclosure relates to a display device, and more particularly, to an organic light emitting display device and a method of manufacturing the same.
Description of the Related Art
An organic light emitting display device (OLED) is a self-luminous display that does not require an additional light source, such as a backlight for a liquid crystal display (LCD). Therefore, organic light emitting display devices can be made lighter and thinner. Further, an organic light emitting display device has advantages in that it is driven with low voltage to consume less power, and that it represents vivid colors and has short response time, wide viewing angle and good contrast ratio (CR). For these reasons, an organic light emitting display device is currently under development as the next generation display.
An organic light emitting display device essentially includes an organic emissive layer in which electrons and holes combine to emit visible rays. Recently, substantial research has been directed toward developing a tandem organic light emitting display device, in which a plurality of organic emissive layers is stacked on one another. It is known that a tandem organic light emitting display device has high efficiency and long lifetime and thus is suitable for realizing a large screen organic light emitting display device.
For a tandem organic light emitting display device having a plurality of organic emissive layers stacked on one another, a reverse-biased diode may be formed between the organic emissive layers. In order to suppress a reverse-biased diode, it is common to dispose a charge generation layer between the plurality of organic emissive layers so as to efficiently supply electrons and holes into the organic emissive layers.
FIG. 1 is a schematic cross-sectional plan view of a tandem organic light emitting display device in the related art.
Referring to FIG. 1, the tandem organic light emitting display device 100 includes a substrate 110, a first electrode 120, a first light emitting unit 130, a charge generation layer 140, a second light emitting unit 150, an electron injection layer 160 and a second electrode 170.
The charge generation layer 140 is disposed between the first light emitting unit 130 and the second light emitting unit 150, each of which includes an organic emissive layer. The charge generation layer 140 adjusts balance of electric charges between the first light emitting unit 130 and the second light emitting unit 150. The second electrode 170 supplies electric charges into the organic emissive layer of the first light emitting unit 130 and the organic emissive layer of the second light emitting unit 150 equally. Thus, light is emitted from each of the first light emitting unit 130 and the second light emitting unit 150.
Typically, the second electrode 170 is extended to edges of the substrate 100 and is connected to Vss supply lines disposed at the edges of the substrate 100. As the second electrode 170 is extended to the edges of the substrate 100, the second electrode 170 often comes in contact with the charge generation layer 140 around the edges of the substrate 110.
If the second electrode 170 comes in contact with the charge generation layer 140, electric charges supplied from the second electrode 170 may fail to be supplied to the organic emissive layer of the second light emitting unit 150. However, the electric charges may be supplied to the organic emissive layer of the first light emitting unit 130 via the charge generation layer 140. When this happens, the electric charges from the second electrode 170 are not equally supplied to the first light emitting unit 130 and the second light emitting unit 150 but are supplied to the first light emitting unit 130 too much. As a result, more light is emitted from the edges of the substrate 100, such that the organic emissive layer of the first light emitting unit 130 is likely to be degraded. Accordingly, the lifetime of the organic light emitting display device 100 is also significantly shortened. The issue of failing to balance electric charges between the first light emitting unit 130 and the second light emitting unit 150 as the second electrode 170 comes in contact with the charge generation layer 140 especially becomes serious as the temperature increases since electric charges become more active.